Camera system and camera body

ABSTRACT

A camera system includes an interchangeable lens and a camera body. The camera body includes an imaging unit, a contrast detection unit, a defocusing amount detection unit, and a body microcomputer. The contrast detection unit is configured to detect a contrast value from an image signal of a subject acquired by the imaging unit, and is configured to detect the focal state of an optical image on the basis of the contrast value. The defocusing amount detection unit is configured to detect the focal state of the optical image by phase difference detection method. The body microcomputer is configured to select either the contrast detection unit or the defocusing amount detection unit on the basis of lens information on the interchangeable lens side.

TECHNICAL FIELD

The present invention relates to a camera system, and more particularlyto a single lens reflex digital camera.

BACKGROUND ART

Single lens reflex digital cameras have rapidly grown in popularity inrecent years. With these single lens reflex digital cameras, when asubject is observed through an optical viewfinder, the light incident onthe imaging optical system is reflected by a reflecting mirror disposedalong the optical path, and is guided to the viewfinder optical system.As a result, the subject image is converted by a pentaprism or the likeinto an erect image and guided to the viewfinder optical system. Thisallows the user to view the subject image formed by the imaging opticalsystem through the optical viewfinder. Thus, the reflecting mirror isusually disposed along the optical path.

Meanwhile, when an optical image of the subject is converted into animage signal, the reflecting mirror is retracted from the optical pathso that the light from the imaging optical system will be incident on animaging element. As a result, opto-electric conversion is performed bythe imaging element, and image data about the subject is obtained. Whenimaging is complete, the reflecting mirror is returned to its homeposition along the optical path. With a single-lens reflex camera, thisoperation of the reflecting mirror is the same regardless of whether thecamera is a conventional silver halide camera or a digital camera.

However, when the home position of the reflecting mirror lies in theoptical path, the light from the imaging optical system is not incidenton the imaging element. Therefore, in the case of a digital camera, amonitor photography mode, in which the user uses a liquid crystalmonitor to view the subject, is not possible, and a camera system suchas this is inconvenient for a beginner unaccustomed to photography.

In view of this, a single-lens reflex digital camera has been proposedwith which a liquid crystal monitor can be used during image capture(see Patent Citation 1, for example). With this camera system, inmonitor photography mode, the reflecting mirror is retracted from theoptical path and the light from the imaging optical system is incidenton the imaging element. This allows the subject to be viewed on theliquid crystal monitor.

Patent Citation 1: Japanese Laid-Open Patent Application 2001-125173

DISCLOSURE OF INVENTION

With a conventional single lens reflex digital camera, phase differencedetection is employed, for example, as the autofocus (AF) mode. Withphase difference detection, light from the imaging optical system isguided to a focal detection unit by a sub-mirror provided to thereflecting mirror, and the amount of defocus is detected. Focaladjustment is performed automatically by driving the focus lens groupaccording to this defocus amount.

However, when the autofocus method is phase difference detection, evenin monitor photography mode in which a liquid crystal monitor is used,when focal adjustment is performed the reflecting mirror first has to beplaced along the optical path and the light has to be guided to thefocal detection unit.

Meanwhile, if the reflecting mirror is placed in the optical path, theoptical path to the imaging element is blocked, and the video displaybeing shown on the liquid crystal monitor is interrupted every timefocal adjustment is performed. Accordingly, there is the risk that theuser may lose sight of the subject and miss a photography opportunityduring focal adjustment.

Thus, conventional camera systems were not convenient to use in monitorphotography mode.

It is an object of the present invention to improve the convenience ofmonitor photography mode in a camera system.

The camera system according to a first aspect is a camera system forphotographing a subject, comprising an interchangeable lens and a camerabody. The interchangeable lens includes an imaging optical system, afocal adjuster, and a lens controller. The imaging optical system isconfigured to form an optical image of the subject. The focal adjusteris configured to optically adjust the focal state of the optical image.The lens controller is configured to control the operation of the focaladjuster. The camera body includes an imaging unit, a first focaldetector, a second focal detector, and a body controller. The imagingunit is configured to convert an optical image of a subject into animage signal. The first focal detector is configured to detect acontrast value from the image signal and is configured to detect thefocal state of the optical image on the basis of the contrast value. Thesecond focal detector is configured to detect the focal state of theoptical image by phase difference detection method on the basis of theoptical image. The body controller is configured to control theoperation of the imaging unit. The body controller is configured to sendand receive information to and from the lens controller. The lenscontroller has lens information related to the interchangeable lens. Thebody controller includes a determination part and a selector. Thedetermination part is configured to determine whether or not the focaladjuster is compatible with the first focal detector on the basis of thelens information. The selector is configured to select either the firstor second focal detector on the basis of the determination result of thedetermination part.

This camera system includes a first focal detector that performs focaldetection by what is called a contrast detection method, and a secondfocal detector is configured to perform focal detection by what iscalled a phase difference detection method. The selector of the bodycontroller is configured to select either the first or second focaldetector on the basis of whether or not the focal adjuster is compatiblewith the first focal detector. Accordingly, when the interchangeablelens is compatible with a contrast detection method, the first focaldetector can be selected as the focal detector installed in the camerabody. As a result, there is no need for a reflecting mirror to bedisposed in the optical path during focal adjustment as with a phasedifference detection method. Consequently, in monitor photography mode,in which the subject is viewed on a liquid crystal monitor, focaladjustment can be performed without a video image of the subject beinginterrupted, and this improves the convenience of the monitorphotography mode.

The camera system according to a second aspect is the camera systemaccording to the first aspect, wherein, if the determination partdetermines that the focal adjuster is not compatible with the firstfocal detector, the selector is configured to select the second focaldetector.

The camera system according to a third aspect is the camera systemaccording to the second aspect, wherein the focal adjuster includes afocus lens group included in the imaging optical system, and a positiondetector configured to detect the position of the focus lens group. Thelens information includes one or more of the following: information foridentifying the interchangeable lens, information related to whether ornot there is a lens shift tolerance range for the focus lens group, andinformation related to the specifications of the position detector.

The camera system according to a fourth aspect is the camera systemaccording to the third aspect, wherein the position detector includes anabsolute position detector configured to detect the position of thefocus lens group with respect to a movable range, and a relativeposition detector configured to detect the movement amount and movementdirection of the focus lens group. The relative position detector isconfigured to detect the movement direction of the focus lens group.When the first focal detector is used for focal adjustment, the focaladjustment is performed on the basis of only the information obtained bythe relative position detector, out of the information obtained by theabsolute position detector and the relative position detector.

The camera system according to a fifth aspect is the camera systemaccording to the fourth aspect, wherein the camera body further includesan operation unit that is connected to the body controller and thatallows information to be inputted from the outside. When thedetermination part determines that the focal detector is compatible withthe first focal detector, the selector selects either the first orsecond focal detector on the basis of the information inputted from theoperation unit.

The camera system according to a sixth aspect is the camera systemaccording to the first aspect, wherein the focal adjuster includes afocus lens group included in the imaging optical system, and a positiondetector configured to detect the position of the focus lens group. Theselector is configured to select the first focal detector when the focuslens group has a lens shift tolerance range that allows movement backand forth in the optical axis direction beyond the standard range fromthe nearest focal position to the infinity focal position.

The camera system according to a seventh aspect is the camera systemaccording to the first aspect, wherein the focal adjuster includes afocus lens group included in the imaging optical system, and a positiondetector configured to detect the position of the focus lens group. Theselector selects the first focal detector when the focus lens group hasa lens shift tolerance range that allows movement back and forth in theoptical axis direction beyond the standard range from the nearest focalposition to the infinity focal position, and the position detector ofthe interchangeable lens is configured to determine the movementdirection of the focus lens.

The camera system according to an eighth aspect is the camera systemaccording to the first aspect, wherein the focal adjuster includes afocus lens group included in the imaging optical system, and a positiondetector configured to detect the position of the focus lens group. Theselector selects the first focal detector when the focus lens group hasa lens shift tolerance range that allows movement back and forth in theoptical axis direction beyond the standard range from the nearest focalposition to the infinity focal position, and the position detector is atwo-phase encoder.

The camera system according to a ninth aspect is the camera systemaccording to the first aspect, wherein, if the determination partdetermines that the focal adjuster is compatible with the first focaldetector, the selector selects the first focal detector, regardless ofwhether or not the photography mode is a monitor photography mode.

The camera system according to a tenth aspect is the camera systemaccording to the first aspect, wherein, if the determination partdetermines that the focal adjuster is compatible with the first focaldetector, and if the photography mode is a monitor photography mode, aquick return mirror is retracted from the optical path of the imagingoptical system.

The camera system according to an eleventh aspect is used in a camerasystem for capturing an image of a subject and allows the attachment ofan interchangeable lens having an imaging optical system. This camerabody comprises an imaging unit, a first focal detector, a second focaldetector, and a body controller. The imaging unit is configured toconvert an optical image of the subject into an image signal. The firstfocal detector is configured to detect a contrast value from the imagesignal and is configured to detect the focal state of the optical imageon the basis of the contrast value. The second focal detector isconfigured to detect the focal state of the optical image by phasedifference detection method on the basis of the optical image. The bodycontroller is configured to control the operation of the imaging unit.The interchangeable lens includes an imaging optical system, a focaladjuster, and a lens controller. The imaging optical system isconfigured to form an optical image of the subject. The focal adjusteris configured to optically adjust the focal state of the optical image.The lens controller is configured to control the operation of the focaladjuster. The body controller is configured to send and receiveinformation to and from the lens controller. The lens controller haslens information related to the interchangeable lens. The bodycontroller includes a determination part and a selector. Thedetermination part determines whether or not the focal adjuster iscompatible with the first focal detector on the basis of the lensinformation. The selector is configured to select either the first orsecond focal detector on the basis of the determination result of thedetermination part.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall diagram of the constitution of a camera system 1;

FIG. 2 is a simplified diagram of the constitution of a camera body 3;

FIG. 3 is a diagram illustrating an example of determination processingperforming by the camera body and lens information;

FIG. 4 is a concept diagram of imaging with the camera system 1;

FIG. 5 is a flowchart of selection by the focal detection unit;

FIG. 6 is a diagram illustrating the operation of the focus lens in acontrast detection method;

FIG. 7 is a diagram illustrating an example of the presetting of a pulsecounter value in the relative position detector by the absolute positiondetector;

FIG. 8 is a diagram illustrating preset error;

FIG. 9 is a diagram illustrating the effect of preset error in acontrast detection method;

FIG. 10 is a diagram illustrating relative position detection bycontrast detection method (no presetting);

FIG. 11 is a diagram illustrating determination of the drive directionusing the relative position detector (single-phase);

FIG. 12 is a diagram illustrating determination of the drive directionusing the relative position detector (two-phase); and

FIG. 13 is a flowchart of selection by the focal detection unit inanother embodiment.

EXPLANATION OF REFERENCE

-   1 single lens reflex camera system-   2 interchangeable lens-   3 camera body-   4 quick return mirror-   5 defocusing amount detection unit (second focal detector)-   12 body microcomputer (body controller)-   20 lens microcomputer (lens controller)-   24 focus lens group-   25 focus lens group controller-   25 a linear position sensor (absolute position detector)-   25 b encoder (relative position detector)-   31 contrast detection unit (first focal detector)-   45 determination part-   46 selector-   71 imaging unit-   72 image display unit-   73 image storage unit

BEST MODE FOR CARRYING OUT THE INVENTION

The camera system according to the present invention will now bedescribed through reference to the drawings. Components that havesubstantially the same function will be numbered the same and redundantdescriptions will be omitted.

The subject side of the camera body will be referred to as the front inthis text, and corresponds to the left direction in FIG. 1, for example.The opposite side of the camera body from the subject, that is, theimaging element side with respect to the imaging optical system, will bereferred to as the rear, and corresponds to the right direction inFIG. 1. The direction corresponding to upward in the vertical directionof a captured image when the lengthwise direction of the captured imageis horizontal will be referred to as the upper side, and corresponds tothe up direction in FIG. 1. Usually, the side where the release buttonis disposed on the camera body corresponds to the upper side. Theopposite direction from the upper side will be referred to as the lowerside, and corresponds to the down direction in FIG. 1. The faces of thevarious components on the front, rear, upper, and lower sides will bereferred to as the front face, rear face, upper face, and lower face,respectively.

1: Overall Configuration of Single Lens Reflex Camera System

The camera system according to the first embodiment of the presentinvention will be described through reference to FIGS. 1 and 2. FIG. 1is an overall diagram of the constitution of a camera system 1, and FIG.2 is a simplified diagram of the constitution of a camera body 3.

As shown in FIG. 1, the camera system 1 is a system used in aninterchangeable lens type of single lens reflex digital camera, andmainly comprises a camera body 3 having the primary function of thecamera system 1, and an interchangeable lens 2 that is removablyattached to the camera body 3. The interchangeable lens 2 is mounted ona lens mount 70 provided to the front face of the camera body 3.

1.1: Camera Body

The camera body 3 mainly comprises an imaging unit 71 for forming animage of a subject, a body microcomputer 12 serving as a body controllerfor controlling the operation of the various components such as theimaging unit 71, an image display unit 72 for displaying the capturedimage and various kinds of information, an image holder 73 for holdingimage data, a viewfinder optical system 19 through which the subject canbe seen, and a nonvolatile memory 53. The camera body 3 has a contrastdetection unit 31 serving as a first focal detector, and a defocusingamount detection unit 5 serving as a second focal detector, so as toafford compatibility with two kinds of autofocusing function.

The imaging unit 71 mainly comprises a quick return mirror 4 for guidingincident light to the viewfinder optical system 19 and the defocusingamount detection unit 5, an imaging sensor 11 such as a CCD forperforming opto-electric conversion, a shutter unit 10 for adjusting theexposure state of the imaging sensor 11, a shutter controller 14 forcontrolling the drive of the shutter unit 10 on the basis of a controlsignal from the body microcomputer 12, and an imaging sensor controller13 for controlling the operation of the imaging sensor 11.

The body microcomputer 12 is a control device serving as the functionalcenter of the camera body 3, and controls various sequences. Morespecifically, the body microcomputer 12 is equipped with a CPU, ROM, andRAM, and the body microcomputer 12 can perform many different functionswhen programs held in the ROM are read into the CPU. For instance, thebody microcomputer 12 has the function of detecting that theinterchangeable lens 2 has been mounted on the camera body 3, thefunction of automatically selecting whether to use the contrastdetection unit 31 or the defocusing amount detection unit 5, and so on.As shown in FIG. 1, the body microcomputer 12 is connected to thevarious components provided to the camera body 3.

The image display unit 72 comprises a liquid crystal monitor 16 forimage display, and an image display controller 15 for controlling theoperation of the liquid crystal monitor 16. The image holder 73comprises an image recording and reproduction unit 18 for recording andreproducing captured images to and from a card-type recording medium(not shown), for example, and an image recording controller 17 forcontrolling the operation of the image recording and reproduction unit18.

The quick return mirror 4 comprises a main mirror 4 a capable ofreflecting and transmitting incident light, and a sub-mirror 4 b that isprovided on the rear face side of the main mirror 4 a and reflectstransmitted light from the main mirror 4 a, and can be flipped upoutside the optical path X by a quick return mirror controller 32. Thisincident light is split into two beams by the main mirror 4 a, and thereflected beam is guided to the viewfinder optical system 19. Thetransmitted beam, meanwhile, is reflected by the sub-mirror 4 b andutilized as an autofocusing light beam by the defocusing amountdetection unit 5 (discussed below). During normal photography, the quickreturn mirror 4 is flipped up outside the optical path X by the quickreturn mirror controller 32, and the shutter unit 10 is opened, so thatan image of the subject is formed on the imaging face of the imagingsensor 11. When photography is not in progress, as shown in FIG. 1, thequick return mirror 4 is disposed in the optical path X, and the shutterunit 10 is closed.

The contrast detection unit 31 is used for detecting the focal state bywhat is called a contrast detection method, and detects a contrast valuewith respect to the position of a focus lens group 24 from an imagesignal obtained by the imaging sensor 11. The body microcomputer 12calculates the focal position on the basis of the contrast valuedetected by the contrast detection unit 31.

Meanwhile, the defocusing amount detection unit 5 is used for detectingthe focal state by what is called a phase difference detection method,and detects the focal position on the basis of light reflected by thesub-mirror 4 b. With this camera system 1, either the contrast detectionunit 31 or the defocusing amount detection unit 5 is automaticallyselected at the time of image capture according to the specifications ofthe interchangeable lens 2. The automatic selection of the focaldetection unit will be discussed below.

The viewfinder optical system 19 comprises a viewfinder screen 6 wherean image of the subject is formed, a pentaprism 7 for converting thesubject image into an erect image, an eyepiece lens 8 for guiding theerect image of the subject to a viewfinder window 9, and the viewfinderwindow 9 through which the user can see the subject.

As shown in FIG. 2, the camera body 3 is provided with a power switch 52for switching the power on and off to the camera system 1, and a releasebutton 50 operated by the user during focusing and release. When thepower switch 52 is used to turn on the power, power is supplied to thevarious components of the interchangeable lens 2 and the camera body 3.

The nonvolatile memory 53 holds various kinds of information related tothe camera body 3 (body information). This body information includes,for example, information related to the model, for identifying thecamera body 3, such as the name of the manufacturer of the camera body3, the date of manufacture, the model number, the version of softwareinstalled in the body microcomputer 12, and information related tofirmware updates. Further, this body information may be stored in amemory unit 36 in the body microcomputer 12 instead of in thenonvolatile memory 53. The interchangeable lens 2 having body mount 80is removably attached to a lens mount 70.

1.2: Interchangeable Lens

As shown in FIG. 1, the interchangeable lens 2 mainly comprises animaging optical system L for forming an image of a subject, a focaladjuster 40 for performing focusing, an aperture adjuster 41 foradjusting the aperture, a lens image blur corrector 28, a lensmicrocomputer 20 serving as a lens controller for controlling theoperation of the interchangeable lens 2, a nonvolatile memory 52, and abody mount 80 that can be attached to the lens mount 70. The lens imageblur corrector 28 corrects image blur attributable to shaking of thecamera system 1 by adjusting the optical path.

The focal adjuster 40 mainly comprises the focus lens group 24 that isprovided drivably in a direction along the optical axis and that adjuststhe focus by moving in a direction along the optical axis, and a focuslens group controller 25 for controlling the drive of the focus lensgroup 24.

The focus lens group controller 25 has a drive motor (not shown) such asa DC motor or an ultrasonic motor, and a drive mechanism (not shown)that converts the rotary motion of the drive motor into the linearmotion of the focus lens group 24.

The drive motor and drive mechanism make it possible for the focus lensgroup 24 to move in a direction along the optical axis within a standardrange F from the nearest focal position F1 to the infinity focalposition F2 (see FIG. 6). The standard range F is a range set as thestandard for the interchangeable lens 2, and within the standard rangeF, the interchangeable lens 2 satisfies aspects of lens performance suchas resolution, amount of peripheral light, and distortion.

The focus lens group 24 must be able to move forward and backward in thedirection of the optical axis, sandwiching the focal position, for thesake of focal position detection by the contrast method discussed below.Accordingly, the movable range H of the focus lens group 24 has lensshift tolerance ranges H1 and H2 forward and backward beyond theabove-mentioned standard range F. The movable range H is the range overwhich the focus lens group 24 is able to move, and is determined by theconfiguration of the drive mechanism of the focus lens group controller25, for example. Thus, the focus lens group 24 is able to move in thedirection of the optical axis within a movable range H that is widerthan the standard range F.

The focus lens group controller 25 has a linear position sensor 25 aserving as an absolute position detector, and an encoder 25 b serving asa relative position detector.

The linear position sensor 25 a is used to detect the position (absoluteposition) of the focus lens group 24 in the direction of the opticalaxis within the movable range H. The linear position sensor 25 a makesuse of a varistor, and utilizes the output voltage with respect to thechange in resistance to acquire position information for the focus lensgroup 24.

The encoder 25 b is a sensor for detecting the amount of movement of thefocus lens group 24 in the direction of the optical axis, and is arotary pulse encoder, for example. More precisely, the encoder 25 b isable to detect the amount of rotation of the drive motor of the focuslens group controller 25. The amount of movement of the focus lens group24 can be ascertained by detecting the amount of rotation of the drivemotor. In addition to being the encoder 25 b, the relative positiondetector can also be a photosensor, a MR element (magneto-resistanceelement), Hall element, a PSD (position sensitive detector), or thelike.

The lens microcomputer 20 calculates the amount of movement of the focuslens group 24 on the basis of the output of the encoder 25 b. Thisallows the relative position of the focus lens group 24 (the change inits position) to be ascertained.

The encoder 25 b is a two-phase encoder, and alternately outputs binarysignals at an equal pitch according to the position of the focus lensgroup 24 in the direction of the optical axis. With the encoder 25 b,since the phase of the signals deviates, the movement direction can bedetected in addition to the movement amount, as shown in FIG. 9. How theencoder 25 b detects the movement direction will be discussed below.

The aperture adjuster 41 mainly comprises an aperture unit 26 foradjusting the aperture or opening, and an aperture controller 27 forcontrolling the operation of the aperture unit 26.

The lens image blur corrector 28 mainly comprises an image blurcorrection lens group 22 and an image blur correction unit drivecontroller 23. The image blur correction unit drive controller 23 is aunit that drives and controls the image blur correction lens group 22,and moves the image blur correction lens group 22 up, down, left, andright within a plane perpendicular to the optical axis of the imagingoptical system L. Also, the amount of shake of the camera system 1 isdetected by a shake detection unit 21. For example, the amount ofmovement of the image blur correction lens group 22 is decided by thelens microcomputer 20 on the basis of the amount of shake that isdetected.

The lens microcomputer 20 is a control device serving as the functionalcenter of the interchangeable lens 2, and is connected to the variouscomponents mounted in the interchangeable lens 2. More specifically, thelens microcomputer 20 is equipped with a CPU, ROM, and RAM, and canperform many different functions when programs held in the ROM are readinto the CPU. Also, the body microcomputer 12 and the lens microcomputer20 are electrically connected via electrical contacts (not shown)provided to the lens mount 70 and the body mount 80, respectively, whichallows them to exchange information. Communication between thesemicroprocessors may also be accomplished by optical communication orwireless electromagnetic waves. The lens microcomputer 20 is connectedto the various components provided to the interchangeable lens 2.

The nonvolatile memory 52 holds various kinds of information related tothe interchangeable lens 2 (lens information). This lens informationincludes, for example, information related to the model, for identifyingthe interchangeable lens 2, such as the name of the manufacturer of theinterchangeable lens 2, the date of manufacture, the model number, theversion of software installed in the lens microcomputer 20, andinformation related to firmware updates (lens specifying information);information related to whether or not the focal adjuster 40 iscompatible with a contrast detection method; and so forth. Thenonvolatile memory 52 can hold information that is sent from the bodymicrocomputer 12. This information may be held in a memory unit in thelens microcomputer 20 instead of in the nonvolatile memory 52.

Automatic Autofocus Selection Function

With the camera system 1, either phase difference detection or contrastdetection is selected as the autofocusing method, according to thespecifications of the interchangeable lens 2 and the use intended by theuser.

More specifically, as shown in FIG. 2, the body microcomputer 12 has adetermination part 45 and a selector 46. The determination part 45determines whether or not the focal adjuster 40 is compatible with thecontrast detection unit 31 on the basis of lens information. Thedetermination part 45 also determines whether or not the camera system 1is in monitor photography mode. The selector 46 selects either contrastdetection or phase difference detection as the autofocusing method onthe basis of the determination result of the determination part 45.Specifically, the selector 46 automatically selects either the contrastdetection unit 31 or the defocusing amount detection unit 5 as the focaldetection unit.

As discussed above, the lens information includes information related towhether or not the focal adjuster 40 is compatible with a contrastdetection method. More precisely, if the focal adjuster 40 is compatiblewith a contrast detection method, information to that effect is storedat a specific address in the lens information, and the bodymicrocomputer 12 determines whether or not the focal adjuster 40 iscompatible with a contrast detection method on the basis of theinformation stored in at a specific address.

For example, if the determination part 45 determines that there iscompatibility, the selector 46 selects the contrast detection method,that is, selects the contrast detection method as the focal detectionunit. In this case, focal detection during photography is carried out bythe contrast detection unit 31. On the other hand, if the determinationpart 45 determines that there is incompatibility, the selector 46selects the phase difference detection method, that is, selects thedefocusing amount detection unit 5 as the focal detection unit. In thiscase, focal detection during photography is carried out by thedefocusing amount detection unit 5.

For example, as shown in FIG. 3, a type A interchangeable lens iscompatible with contrast detection as well as phase differencedetection. A type B interchangeable lens is compatible only with phasedifference detection. The lens information includes information such as“type A” or “type B” as the type of lens, and “1: compatible” or “0:incompatible” as information about compatibility with contrastdetection. The focal detection method is selected on the basis of thisinformation. For instance, with a type A interchangeable lens, thecontrast detection method is selected if an image is to be captured inmonitor photography mode. With a type B interchangeable lens, the phasedifference detection method is selected regardless of the photographymode.

3: Operation of Camera System

The operation of the camera system 1 during imaging will be describedthrough reference to FIGS. 1 to 5. FIG. 4 is a concept diagram ofimaging with the camera system 1. FIG. 5 is a flowchart of selection bythe focal detection unit.

3.1: Viewfinder Photography Mode

As shown in FIGS. 1 and 4, in viewfinder photography mode in which theuser looks through the viewfinder window 9 to capture an image, the mainmirror 4 a is disposed along the optical path. Accordingly, light fromthe subject (not shown) is transmitted through the imaging opticalsystem L and incident on the main mirror 4 a, which is a semitransparentmirror. Part of the light incident on the main mirror 4 a is reflectedby the main mirror 4 a and is incident on the viewfinder screen 6, andthe rest of the light is transmitted through the main mirror 4 a and isincident on the sub-mirror 4 b. The light incident on the viewfinderscreen 6 forms a subject image. This subject image is converted by thepentaprism 7 into an erect image, which is incident on the eyepiece 8.This allows the user to observe an erect image of the subject throughthe viewfinder window 9. Also, the light incident on the sub-mirror 4 bis reflected and is incident on the defocusing amount detection unit 5.

When the user presses the release button 50 halfway down, power issupplied to the body microcomputer 12 and the various units in thecamera system 1, and the body microcomputer 12 and the lensmicrocomputer 20 are activated. The body microcomputer 12 and the lensmicrocomputer 20 are programmed so as to exchange information back andforth upon activation via the electrical contacts (not shown) of thelens mount 70. For instance, lens information related to theinterchangeable lens 2 is sent from the memory unit 29 of the lensmicrocomputer 20 to the body microcomputer 12, and this lens informationis held in the memory unit 36 of the body microcomputer 12. At thispoint, as shown in FIG. 5, the body microcomputer 12 also receivesinformation related to whether or not the focal adjuster 40 iscompatible with contrast detection (S1). After this, the determinationpart 45 determines whether or not the photography mode is monitorphotography mode (S2). In the case of viewfinder photography mode, themain mirror 4 a must be inserted into the optical path. Therefore, withviewfinder photography mode, the defocusing amount detection unit 5 isselected as the focal detection unit (S5).

Next, the amount of defocus (hereinafter referred to as the Df amount)is acquired by the defocusing amount detection unit 5 on the basis ofthe reflected light from the sub-mirror 4 b. A command is sent from thebody microcomputer 12 to the lens microcomputer 20 so that the focuslens group 24 will be driven by this Df amount. More specifically, thefocus lens group controller 25 is controlled by the lens microcomputer20 and the focus lens group 24 is moved by the Df amount. The Df amountcan be reduced by repeating this focus detection and drive of the focuslens group 24. Once the Df amount is at or below a specific level, it isdetermined by the body microcomputer 12 that the system is focused, andthe drive of the focus lens group 24 is stopped. After this, when therelease button 50 is pressed all the way down by the user, a command issent from the body microcomputer 12 to the lens microcomputer 20 so asto obtain an aperture value calculated on the basis of the output from alight sensor (not shown). The aperture controller 27 is controlled bythe lens microcomputer 20, and the aperture is closed until thedesignated aperture is attained. Simultaneously with the designation ofthe aperture value, the quick return mirror 4 is retracted from theoptical path X by the quick return mirror controller 32. Upon completionof this retraction, a command to drive the imaging sensor 11 isoutputted from the imaging sensor controller 13, and the operation ofthe shutter unit 10 is indicated. The imaging sensor 11 is exposed bythe imaging sensor controller 13 for the length of time of the shutterspeed calculated on the basis of the output from a light sensor (notshown).

Upon completion of this exposure, the imaging sensor controller 13 readsimage data from the imaging sensor 11, and after specific imageprocessing, image data is outputted through the body microcomputer 12 tothe image display controller 15. As a result, the captured image isdisplayed on the liquid crystal monitor 16. Image data is held in astorage medium via the image recording controller 17 and the imagerecording and reproduction unit 18. Upon completion of the exposure, thequick return mirror 4 and the shutter unit 10 are reset to their initialpositions by the body microcomputer 12. A command is issued from thebody microcomputer 12 to the lens microcomputer 20 for the aperturecontroller 27 to reset the aperture to its open position, and resetcommands are sent from the lens microcomputer 20 to the various units.Upon completion of this resetting, the lens microcomputer 20 notifiesthe body microcomputer 12 of the completion of resetting. After the bodymicrocomputer 12 has received the reset completion information and aseries of processing has been completed after the completion ofexposure, it is confirmed that the release button has not been pressed,whereupon the body microcomputer 12 concludes the imaging sequence.

3.2: Monitor Photography Mode

Meanwhile, in monitor photography mode, in which the user captures animage while looking at the liquid crystal monitor 16, an optical imageformed by the imaging optical system L is guided to the imaging sensor11, so the main mirror 4 a is retracted from the optical path.Accordingly, light from the subject (not shown) is transmitted by theimaging optical system L and is incident on the imaging sensor 11. Atthe imaging sensor 11, the optical image is converted into an imagesignal by opto-electrical conversion, and a video image of the subjectis outputted to the liquid crystal monitor 16 on the basis of this imagesignal. This allows the user to capture an image while looking at thelive video image of the subject.

However, when focal adjustment is performed using the defocusing amountdetection unit 5, the main mirror 4 a and the sub-mirror 4 b need to bedisposed along the optical path. This means that in performing focaldetection, there is the risk that light to the imaging sensor 11 will beblocked, the live video image of the subject being shown on the liquidcrystal monitor 16 will be interrupted, and the user will miss aphotography opportunity.

In view of this, with the camera system 1, when in monitor photographymode and when the interchangeable lens 2 is compatible with contrastdetection, the contrast detection method is selected as the focaldetection method. More specifically, when the user presses the releasebutton 50 halfway down, power is supplied to the various components.Lens information related to the interchangeable lens 2 is sent from thememory unit 29 of the lens microcomputer 20 to the body microcomputer12, and this lens information is stored in the memory unit 36 of thebody microcomputer 12. At this point, as shown in FIG. 5, the bodymicrocomputer 12 also receives information related to whether or not thefocal adjuster 40 is compatible with the contrast detection method (S1).

The determination part 45 of the body microcomputer 12 determineswhether or not the photography mode is the monitor photography mode(S2). In this case, since the photography mode is the monitorphotography mode, it is determined whether or not the focal adjuster 40is compatible with contrast detection on the basis of the lensinformation (S3). As discussed above, the lens information includesinformation to the effect that the focal adjuster 40 is compatible withcontrast detection. Therefore, the determination part 45 determines thatthe focal adjuster 40 is compatible with contrast detection. Thecontrast detection unit 31 is selected as the focal detection unit bythe selector 46 on the basis of this determination result (S4).

In this case, the main mirror 4 a is held in its retracted state by thequick return mirror controller 32, and a contrast value is detected onthe basis of the image signal obtained by the imaging sensor 11. Whilethe focus lens group 24 is being driven in the direction of the opticalaxis by the focus lens group controller 25, a contrast value is detectedby the contrast detection unit 31. The position information about thefocus lens group 24 from the focus lens group controller 25 and thecontrast value from the contrast detection unit 31 are stored in thememory unit 36 of the body microcomputer 12, for example. As a result,the relation between the position of the focus lens group 24 and thecontrast value can be ascertained.

In this case, the image at which the contrast value is at its peak isthe image that is focused best. Therefore, the focus lens group 24 isfinally driven by the focus lens group controller 25 to a positioncorresponding to the peak of the contrast value, and focal adjustment isconcluded. Upon conclusion of the focal adjustment, subject image datais acquired by the imaging unit 71 just as in the viewfinder photographymode.

4: Contrast Detection Method

The contrast detection method used by the camera system 1 will now bedescribed through reference to FIG. 6. FIG. 6 is a diagram illustratingthe operation of the focus lens in this contrast detection method.

As shown in FIG. 6, with this contrast detection method, in detecting acontrast value, the focus lens group 24 moves in the direction of theoptical axis between a detection start position F11 and a detection stopposition F12. More specifically, first, the focus lens group 24 isdriven by the focus lens group controller 25 in a B direction (to theright in FIG. 6) from the detection start position F11 to the detectionstop position F12 (first focus drive operation). Here, a contrast valueis detected at each position of the focus lens group 24 by the contrastdetection unit 31. At this point position information for the focus lensgroup 24 from the focus lens group controller 25 and the contrast valuefrom the contrast detection unit 31 are stored in the memory unit 36 ofthe body microcomputer 12. Also, the position of the focus lens group 24corresponding to the contrast value is stored in the memory unit 36 ofthe body microcomputer 12.

Next, the focus lens group 24 is driven backward (A direction) by thefocus lens group controller 25 from the detection stop position F12 soas to pass the position corresponding to the peak contrast value (secondfocus drive operation). When the movement direction of the focus lensgroup 24 changes, a phenomenon occurs whereby backlash (a gap formedbetween the teeth of gears) in the drive mechanism (not shown) of thefocus lens group controller 25 allows the drive motor to rotate butprevents the focus lens group 24 from moving. Accordingly, immediatelyafter the focus lens group 24 has changed its direction of movement,when the drive motor rotates, the pulse count of the encoder 25 bchanges, but the focus lens group 24 does not move because of backlash.

To reduce the effect of this backlash, the focus lens group 24 is drivenby the focus lens group controller 25 so as to go past the peak contrastvalue (second focus drive operation), and the movement direction of thefocus lens group 24 is switched again. At this point, any error in theposition of the focus lens group 24 caused by backlash is cancelled outin the re-switching of the movement direction of the focus lens group24. After this, the focus lens group 24 is driven by the focus lensgroup controller 25 to a position corresponding to the peak contrastvalue, and the focusing operation is ended (third focus driveoperation). The decrease in positional accuracy caused by backlash canthus be suppressed by the first to third focus drive operations.

5: Position Detection Method

To improve the precision of focal adjustment, accurate positioninformation about the focus lens group is necessary. How the position ofthe focus lens group 24 is detected by the focus lens group controller25 will now be described. For example, in the case of phase differencedetection, the amount of movement of the focus lens group 24 iscalculated by the body microcomputer 12 on the basis of the Df amountobtained by the defocusing amount detection unit 5 and the currentposition information about the focus lens group 24. The focus lens group24 is driven by the focus lens group controller 25 on the basis of thecalculated movement amount, and the focus lens group 24 is disposed atthe focal position. Accordingly, with a phase difference detectionmethod, absolute position information about the focus lens group 24 isnecessary in the operation of the defocusing amount detection unit 5,and the precision of this absolute position information affects theprecision of the focal adjustment.

However, with a single lens reflex digital camera, since the drive motorthat drives the focus lens group is not the stepping motor that is usedin an ordinary digital camera, but instead a DC motor, ultrasonic motor,or the like, the absolute position of the focus lens group cannot beascertained with a drive motor alone.

In view of this, an absolute position detector and a relative positiondetector are installed in the interchangeable lens of a single lensreflex digital camera. The absolute position detector can detect theabsolute position of the focus lens group within its movable range. Therelative position detector can detect the amount of movement of thefocus lens group. As discussed above, with this embodiment, the linearposition sensor 25 a and the encoder 25 b are installed in theinterchangeable lens 2 as an absolute position detector and a relativeposition detector, respectively.

In general, an absolute position detector has relatively low resolution,but the resolution of a relative position detector is higher than theresolution of an absolute position detector. Therefore, basically theabsolute position of the focus lens group is ascertained by the absoluteposition detector, and the pulse count of the relative position detectoris preset to match the rise of the pulse of the absolute positiondetector. This means that the low resolution of the absolute positiondetector can be compensated for by the relative position detector byascertaining the precise position with the relative position detectorusing the preset position as a reference.

The presetting of the relative position detector will now be described.Position information for the focus lens group basically uses the outputpulse of the absolute position detector as a reference, but the pulsecount of the relative position detector is preset simultaneously withthe rise of the pulse of the absolute position detector. For example, asshown in FIG. 7, the pulses of the relative position detector areautomatically preset to 6, 11, and 16 with respect to the pulses 1, 2,and 3 of the absolute position detector. Consequently, the preciseposition of the focus lens group can be ascertained by the relativeposition detector using the pulses of the absolute position detector asa reference.

However, when focusing is performed by contrast detection method usingthis position detection method, preset error which occurs during thepresetting of the relative position detector is a problem.

The preset error will now be described through reference to FIG. 8. FIG.8 is a diagram illustrating the output pulses of the relative positiondetector with preset error.

In FIG. 8, the ideal state of the rise timing of pulses from theabsolute position detector is indicated by the solid lines, while statesin which the rise of the pulses is faster and slower than that of theideal state are indicated by dotted lines. As shown in FIG. 8, in anideal state, if the pulse count of the relative position detector ispreset to “6,” the pulse count of the relative position detector willincrease continuously from before the pulse rise of the absoluteposition detector. However, if there is error in the timing of the pulserise, the pulse count of the relative position detector ends up beingforcibly preset to “6.” Therefore, error occurs in the pulse count, andan accurate count of the number of pulses cannot be obtained. With phasedifference detection, the command is updated so that the Df amountgradually decreases, so there is no major problem with this preseterror.

With contrast detection, however, this present error greatly affectspositioning precision. The effect that preset error has on positioningprecision will be described through reference to FIG. 9. FIG. 9 showsthe effect of preset error on positioning precision. The presetconditions are set as follows.

a) In the first and second focus drive operations, the focus lens group24 is stopped after a pulse count of four after passing the positioncorresponding to the peak.

b) In presets 1 and 2, which are preset timing with the absoluteposition detector, the value of the relative position detector is presetto “6” on the way out (during the first focus drive operation), and to“5” on the way back (during the second focus drive operation).

(1) First Focus Drive Operation

First, the count of the number of pulses of the relative positiondetector is started from the start of drive of the drive motor. Thepulse count of the relative position detector is preset to “6” at thetiming of preset 1. At the point of preset 1, presetting is performed asset, and the count of pulses of the relative position detector goescontinuously from the start of drive. The body microcomputer 12determines that the position corresponding to the pulse count “7”corresponds to the peak contrast value when the pulse count is in the“8” position, and the pulse count “7” corresponding to the peak isstored in the memory unit 36 of the body microcomputer 12. According tothe set conditions, the focus lens group 24 stops at the position of apulse count of “11,” which is four pulses ahead of the positioncorresponding to the peak contrast value.

(2) Second Focus Drive Operation

The drive motor is reversed to a pulse count of “3,” which is fourpulses (a set condition) back from the pulse count of “7” of the peakposition detected in the first focus drive operation. Immediately afterthe rotational direction of the drive motor is switched, there is nochange in the position of the focus lens group even if the drive motorreverses by two pulses, for example, due to backlash as mentioned above.Specifically, error occurs between the pulse count and the position ofthe focus lens group. For example, as shown in FIG. 9, the effect ofbacklash causes the pulse count to be “5” at the position correspondingto the peak contrast value, so there is deviation between the pulsecount and the position corresponding to the peak contrast value.

Also, the pulse count is preset to “5” at the timing of preset 2. Here,preset error causes the pulse count to be preset at a different positionfrom the position of the focus lens group at the timing of preset 1.Accordingly, the preset 2 causes the pulse count to be off by one pulse.

According to a set condition, when the pulse count reaches “3,” thefocus lens group controller stops the drive of the focus lens group.

(3) Third Focus Drive Operation

Next, the drive motor of the focus lens group controller begins forwardrotation. Since backlash occurs immediately after the start of forwardrotation, there is no change in the position of the focus lens groupeven if the drive motor rotates forward by two pulses. When backlash iseliminated, the focus lens group is driven by forward rotation of thedrive motor.

According to a set condition, the focus lens group controller 25 stopsthe focus lens group 24 at the position of the pulse count “7,” and thefocal adjustment operation is concluded.

The effect of backlash can thus be reduced by inverting the rotationtwice, but because of preset error, the focus lens group stops at adifferent position from the position corresponding to the peak contrastvalue detected in the first focus drive operation. Accordingly, with acontrast detection method, since the reciprocal motion of the focus lensgroup is repeated, the effect of preset error is magnified, and thislowers the positional precision of the focus lens group. Specifically,the precision of focal adjustment is diminished.

In view of this, with the camera system 1, when focal adjustment isperformed by contrast detection method, position detection is performedusing just the encoder 25 b, rather than using two position detectors,namely, the linear position sensor 25 a and the encoder 25 b, as with aconventional method. FIG. 10 shows an example of the operation of thecamera system 1 when just the encoder 25 b is used.

As shown in FIG. 10, in this case there is no presetting by the linearposition sensor 25 a, and pulse information can be ascertained for theencoder 25 b at all times. Accordingly, error is less likely to occur inthe pulse count, and the focus lens group 24 is positioned accurately atthe position corresponding to the peak contrast value detected in thefirst focus drive operation. Thus performing focal adjustment bycontrast detection method using only the encoder 25 b eliminates theeffect of preset error during focal adjustment. Consequently,positioning precision of the focus lens group 24 is enhanced, and focaladjustment is more precise.

6: Drive Direction Detection Method

Because it is two-phase, the encoder 25 b is also able to determine thedrive direction (forward or reverse). FIG. 11 is a diagram illustratingthe situation when the encoder 25 b is single-phase, and FIG. 12 is adiagram illustrating the situation when the encoder 25 b is two-phase.

As shown in FIG. 11, when the encoder 25 b is single-phase, it can bedetermined whether the drive motor is rotating forward or in reversefrom the input command to the motor during rotation. Therefore, when asignal is inputted to the drive motor, the drive direction and theamount of rotation of the drive motor, that is, the movement amount andmovement direction of the focus lens group 24, can be determined fromthe output pulse from the encoder 25 b and this input signal.

Nevertheless, if the drive motor comes to a stop during inversion,momentum will keep the drive motor from stopping right away even thoughthe drive motor input signal stops, and this momentum will cause thedrive motor to rotate slightly before stopping. Here, the drive motordoes not necessarily always rotate in the same direction until the stopof rotation, and it is also possible that it will rotate in reverse dueto the effect of the drive mechanism. Therefore, when the encoder 25 bis single-phase, if there is no input signal to the drive motor, it ispossible that the drive direction of the drive motor cannot be detectedand error will occur in the pulse count.

As shown in FIG. 12, with this camera system 1, the encoder 25 b istwo-phase. When the encoder 25 b is two-phase, regardless of a motorinput signal, the rotation direction of the motor can always beascertained from the relation between the CH1 pulses and the CH2 pulses.For example, as shown in FIG. 12, when the CH2 pulses are low in achange of the CH1 pulses from low to high, the rotation direction of thedrive motor is forward. When the CH2 pulses are high in a change of theCH1 pulses from high to low, the rotation direction of the drive motoris reverse. Thus, by using a two-phase encoder 25 b, the movement amountand movement direction of the focus lens group 24 can be ascertainedaccurately, and there will be less error between the pulse count and theposition information about the focus lens group 24. Specifically, usinga two-phase encoder 25 b raises focal adjustment precision when thecontrast detection method is selected.

7: Effects

The effects obtained with the camera system 1 are as follows.

(1)

With this camera system 1, the selector 46 of the body microcomputer 12determines whether or not the interchangeable lens 2 (more precisely,the focal adjuster 40) is compatible with a contrast detection method onthe basis of lens information. The selector 46 selects either thecontrast detection method or the phase difference detection method onthe basis of this determination result. Thus, with this camera system 1,the focal detection method is automatically detected according to thespecifications of the interchangeable lens 2.

For instance, when the photography mode is the monitor photography mode,and the interchangeable lens 2 is compatible with the contrast detectionmethod, the selector 46 selects contrast detection as the focaldetection method. Accordingly, there is no need to dispose the quickreturn mirror 4 in the optical path during focal adjustment, as withphase difference detection. Consequently, in monitor photography mode inwhich the subject is viewed on the liquid crystal monitor 16, focaladjustment can be performed without interrupting the video image of thesubject, and this makes the monitor photography mode more convenient touse.

Also, with the camera system 1, when the determination part 45determines that the interchangeable lens 2 is not compatible with thecontrast detection method, the selector 46 selects phase differencedetection as the focal detection method. Consequently, even if theinterchangeable lens 2 is not compatible with contrast detection, focaladjustment can be performed by phase difference detection.

(2)

With this camera system 1, the encoder 25 b is two-phase, and the drivedirection and the amount of rotation of the drive motor can be detectedfrom the output pulses of the encoder 25 b. As a result, if positiondetection is performed with just the encoder 25 b by contrast detectionmethod, there will be no preset error, unlike when position detection isperformed using both the linear position sensor 25 a and the encoder 25b.

Thus using a position detector capable of detecting the movement amountand movement direction of the focus lens group 24 eliminates theoccurrence of present error and improves position detection precision.Consequently, focal adjustment precision can be increased in thecontrast detection method.

8: Other Embodiments

The single lens reflex camera system, camera body, and interchangeablelens according to the present invention are not limited to or by theembodiment given above, and various changes and modifications arepossible without departing from the gist of the present invention.

(1)

In the embodiment given above, when monitor photography mode was usedand the interchangeable lens 2 was compatible with contrast detectionmethod, contrast detection was selected as the focal detection method.However, when the interchangeable lens 2 is compatible with contrastdetection method, regardless of whether or not the photography mode isthe monitor photography mode, contrast detection may be selected as thefocal detection method at the start of photography preparations. Also,when the contrast detection method has been selected and the photographymode is not monitor photography mode, the system may switch to monitorphotography mode and the quick return mirror 4 retracted from theoptical path X by the quick return mirror controller 32.

More specifically, when the user switches on the power to the camerasystem 1, power is supplied to the various components. As shown in FIG.13, selection of the focal detection method begins at this point. Lensinformation related to the interchangeable lens 2 is sent from thememory unit 29 of the lens microcomputer 20 to the body microcomputer12, and this lens information is stored in the memory unit 36 of thebody microcomputer 12. At this point, as shown in FIG. 5, the bodymicrocomputer 12 also receives information related to whether or not thefocal adjuster 40 is compatible with the contrast detection method.

The determination part 45 of the body microcomputer 12 determineswhether or not the focal adjuster 40 is compatible with contrastdetection on the basis of the lens information (S12). As discussedabove, the lens information includes information to the effect that thefocal adjuster 40 is compatible with contrast detection. Therefore, thedetermination part 45 determines that the focal adjuster 40 iscompatible with contrast detection. The selector 46 then selects thecontrast detection unit 31 as the focal detection unit on the basis ofthis determination result (S13). If it is determined on the basis of thelens information that the focal adjuster 40 is not compatible withcontrast detection, the selector 46 selects phase difference detectionas the focal detection unit (S14), and the selection processing isconcluded.

When the contrast detection method is selected, the determination part45 of the body microcomputer 12 determines whether or not thephotography mode is the monitor photography mode (S15). If thedetermination part 45 determines that the photography mode is themonitor photography mode, the selection processing is concluded. In thiscase, the main mirror 4 a is held in its retracted state by the quickreturn mirror controller 32. On the other hand, if the determinationpart 45 determines that the photography mode is not the monitorphotography mode (S15), the mode switches to the monitor photographymode (S16). More specifically, the quick return mirror 4 is retractedfrom the optical path X by the quick return mirror controller 32 (S17).

(2)

In the embodiment given above, the focal detection method wasautomatically selected by the selector 46. However, it is alsoconceivable that the focal detection method will be selected manually bythe user. For example, the constitution may be such that the user canselect the focal detection method by using a control switch (not shown),so that the user can select the focal detection method manually. In thiscase, the preferred focal detection method can be selected according tothe application, such as still or moving pictures, and this makes thecamera system 1 more convenient to use.

(3)

In the embodiment given above, the encoder 25 b was employed as therelative position detector, but the relative position detector is notlimited to this. For instance, in addition to being the encoder 25 b,the relative position detector may be a photosensor, a MR element(magneto-resistance element), a Hall element, a PSD (position sensitivedetector, or the like.

(4)

The selector 46 may select the first focal detector when the focus lensgroup 24 has the lens shift tolerance range H1, in which it can moveforward and backward in the optical axis direction beyond the standardrange F from the nearest focal position F1 to the infinity focalposition F2.

(5)

The selector 46 may select the first focal detector when the focus lensgroup 24 has the lens shift tolerance range H1, in which it can moveforward and backward in the optical axis direction beyond the standardrange F from the nearest focal position F1 to the infinity focalposition F2, and the relative position detector of the interchangeablelens can determine the movement direction of the focus lens group 24.

(6)

The selector 46 may select the first focal detector when the focus lensgroup 24 has the lens shift tolerance range H1, in which it can moveforward and backward in the optical axis direction beyond the standardrange F from the nearest focal position F1 to the infinity focalposition F2, and the relative position detector is a two-phase encoder.

INDUSTRIAL APPLICABILITY

With the single lens reflex camera system according to the presentinvention, autofocusing is possible by contrast method. Therefore, thepresent invention is useful in the field of optical devices.

1-11. (canceled)
 12. A camera system for photographing a subject,comprising: an interchangeable lens including an imaging optical systemconfigured to form an optical image of the subject, a focal adjusterconfigured to adjust optically the focal state of the optical image, anda lens controller configured to control the operation of the focaladjuster; and a camera body including an imaging unit configured toconvert an optical image of the subject into an image signal, a firstfocal detector configured to detect a contrast value from the imagesignal and configured to detect the focal state of the optical image onthe basis of the contrast value, a second focal detector configured todetect the focal state of the optical image by phase differencedetection method on the basis of the optical image, and a bodycontroller configured to control the operation of the imaging unit, thebody controller configured to send and receive information to and fromthe lens controller, the lens controller including lens informationrelated to the interchangeable lens, and the body controller including adetermination part configured to determine whether or not the focaladjuster is compatible with the first focal detector on the basis of thelens information, and a selector configured to select either the firstor second focal detector on the basis of the determination result of thedetermination part.
 13. The camera system according to claim 12,wherein, when the determination part determines that the focal adjusteris not compatible with the first focal detector, the selector selectsthe second focal detector.
 14. The camera system according to claim 13,wherein the focal adjuster includes a focus lens group included in theimaging optical system, and a position detector configured to detect theposition of the focus lens group, and the lens information includes oneor more of the following: information used to identify theinterchangeable lens, information related to whether or not there is alens shift tolerance range for the focus lens group, and informationrelated to the specifications of the position detector.
 15. The camerasystem according to claim 14, wherein the position detector includes anabsolute position detector configured to detect the position of thefocus lens group with respect to a movable range, and a relativeposition detector configured to detect the movement amount and movementdirection of the focus lens group, and when the first focal detector isused for focal adjustment, the focal adjustment is performed on thebasis of only the information obtained by the relative positiondetector, out of the information obtained by the absolute positiondetector and the relative position detector.
 16. The camera systemaccording to claim 15, wherein the camera body further includes anoperation unit connected to the body controller and configured to allowinformation to be inputted from the outside, and when the determinationpart determines that the focal adjuster is compatible with the firstfocal detector, the selector selects either the first or second focaldetector on the basis of the information inputted from the operationunit.
 17. The camera system according to claim 12, wherein the focaladjuster includes a focus lens group included in the imaging opticalsystem, and a position detector configured to detect the position of thefocus lens group, and the selector selects the first focal detector whenthe focus lens group has a lens shift tolerance range arranged to allowmovement back and forth in the optical axis direction beyond a standardrange from a nearest focal position to an infinity focal position. 18.The camera system according to claim 12, wherein the focal adjusterincludes a focus lens group included in the imaging optical system, anda position detector configured to detect the position of the focus lensgroup, and the selector selects the first focal detector when the focuslens group has a lens shift tolerance range arranged to allow movementback and forth in the optical axis direction beyond the standard rangefrom the nearest focal position to the infinity focal position, and theposition detector of the interchangeable lens is configured to determinethe movement direction of the focus lens.
 19. The camera systemaccording to claim 12, wherein the focal adjuster includes a focus lensgroup included in the imaging optical system, and a position detectorconfigured to detect the position of the focus lens group, and theselector selects the first focal detector when the focus lens group hasa lens shift tolerance range arranged to allow movement back and forthin the optical axis direction beyond the standard range from the nearestfocal position to the infinity focal position, and the position detectoris a two-phase encoder.
 20. The camera system according to claim 12,wherein when the determination part determines that the focal adjusteris compatible with the first focal detector, the selector selects thefirst focal detector, regardless of whether or not the photography modeis a monitor photography mode.
 21. The camera system according to claim12, wherein, when the determination part determines that the focaladjuster is compatible with the first focal detector, and when thephotography mode is a monitor photography mode, a quick return mirror isretracted from the optical path of the imaging optical system.
 22. Acamera body used in a camera system for capturing an image of a subjectand to which an interchangeable lens including an imaging optical systemcan be attached, comprising: an imaging unit configured to convert anoptical image of the subject into an image signal; a first focaldetector configured to detect a contrast value from the image signal anddetect the focal state of the optical image on the basis of the contrastvalue; a second focal detector configured to detect the focal state ofthe optical image by phase difference detection method on the basis ofthe optical image; and a body controller configured to control theoperation of the imaging unit, the interchangeable lens including animaging optical system configured to form an optical image of thesubject, a focal adjuster configured to adjust optically the focal stateof the optical image, and a lens controller configured to control theoperation of the focal adjuster, the body controller configured to sendand receive information to and from the lens controller, the lenscontroller including lens information related to the interchangeablelens, and the body controller including a determination part configuredto determine whether or not the focal adjuster is compatible with thefirst focal detector on the basis of the lens information, and aselector configured to select either the first or second focal detectoron the basis of the determination result of the determination part. 23.The camera body according to claim 22, wherein, when the determinationpart determines that the focal adjuster is not compatible with the firstfocal detector, the selector selects the second focal detector.
 24. Thecamera body according to claim 23, wherein the focal adjuster includes afocus lens group included in the imaging optical system, and a positiondetector configured to detect the position of the focus lens group, andthe lens information includes one or more of the following: informationused to identify the interchangeable lens, information related towhether or not there is a lens shift tolerance range for the focus lensgroup, and information related to the specifications of the positiondetector.
 25. The camera body according to claim 24, wherein theposition detector includes an absolute position detector configured todetect the position of the focus lens group with respect to a movablerange, and a relative position detector configured to detect themovement amount and movement direction of the focus lens group, and whenthe first focal detector is used for focal adjustment, the focaladjustment is performed on the basis of only the information obtained bythe relative position detector, out of the information obtained by theabsolute position detector and the relative position detector.
 26. Thecamera body according to claim 25, wherein the camera body furtherincludes an operation unit connected to the body controller andconfigured to allow information to be inputted from the outside, andwhen the determination part determines that the focal adjuster iscompatible with the first focal detector, the selector selects eitherthe first or second focal detector on the basis of the informationinputted from the operation unit.
 27. The camera body according to claim22, wherein the focal adjuster includes a focus lens group included inthe imaging optical system, and a position detector configured to detectthe position of the focus lens group, and the selector selects the firstfocal detector when the focus lens group has a lens shift tolerancerange arranged to allow movement back and forth in the optical axisdirection beyond a standard range from a nearest focal position to aninfinity focal position.
 28. The camera body according to claim 22,wherein the focal adjuster includes a focus lens group included in theimaging optical system, and a position detector configured to detect theposition of the focus lens group, and the selector selects the firstfocal detector when the focus lens group has a lens shift tolerancerange arranged to allow movement back and forth in the optical axisdirection beyond the standard range from the nearest focal position tothe infinity focal position, and the position detector of theinterchangeable lens is configured to determine the movement directionof the focus lens.
 29. The camera body according to claim 22, whereinthe focal adjuster includes a focus lens group included in the imagingoptical system, and a position detector configured to detect theposition of the focus lens group, and the selector selects the firstfocal detector when the focus lens group has a lens shift tolerancerange arranged to allow movement back and forth in the optical axisdirection beyond the standard range from the nearest focal position tothe infinity focal position, and the position detector is a two-phaseencoder.
 30. A camera body used in a camera system for capturing animage of a subject and to which an interchangeable lens including animaging optical system can be attached, comprising: a body mount towhich the interchangeable lens can be attached; an imaging unitconfigured to convert an optical image of the subject formed by theimaging optical system into an image signal; a movable mirror configuredto be in a first state of being positioned in an optical path betweenthe optical system and the imaging unit, and in a second state of beingpositioned outside of the optical path; an image displaying unitconfigured to display an image on the basis of the image signalgenerated by the imaging unit; and a body controller configured tocontrol the image displaying unit to display real-time image based onthe image signals generated by the imaging unit during a monitorphotography mode in which the movable mirror is in the second state; thebody controller configured to differ controlling to perform autofocusingduring the monitor photography mode, in accordance with whether or notthe interchangeable lens attached to the body mount includes a lensshift tolerance range arranged to allow movement of the focus lens groupback and forth in the optical axis direction beyond a standard rangefrom a nearest focal position to an infinity focal position.
 31. Thecamera body according to claim 30, wherein, the body controller isconfigured to perform the autofocusing during the monitor photographymode by detecting a contrast value from the image signal and detectingthe focal state of the optical image on the basis of the contrast value.